Semicoductor device containing an ultra thin dielectric film or dielectric layer

ABSTRACT

An ultra thin dielectric film or dielectric layer on a semiconductor device is disclosed. In one embodiment, an oxide layer is formed over a substrate. A silicon-containing material is deposited over the oxide layer. The deposited material and oxide layer are processed in a plasma to form the dielectric layer or ultra thin dielectric film. The silicon-containing dielectric layer can allow for improved or smaller semiconductor devices. The silicon containing dielectric layer can be fabricated at low temperatures. Improved or smaller semiconductor devices may be accomplished by reducing leakage, increasing the dielectric constant or fabricating at lower temperatures.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.10/273,666 filed Oct. 18, 2002 which is a divisional of U.S. patentapplication Ser. No. 09/653,298 filed Aug. 31, 2000, now U.S. Pat. No.6,521,544 issued Feb. 18, 2003.

This application is related to commonly assigned U.S. Pat. Nos.6,410,968, SEMICONDUCTOR DEVICE WITH BARRIER LAYER, issued Jun. 25,2002, by Powell et al. and 6,576,964, DIELECTRIC LAYER FOR ASEMICONDUCTOR DEVICE HAVING LESS CURRENT LEAKAGE AND INCREASEDCAPACITANCE, issued Jun. 10, 2003, by Powell et al., the disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the field of semiconductors and, moreparticularly, to forming a dielectric layer at a low temperature.

BACKGROUND OF THE INVENTION

There is an increasing demand for semiconductor devices of reduced size.The performance characteristics of semiconductor devices become moreimportant as device size decreases. Accordingly, processes that enhanceperformance characteristics are important to improved semiconductorfabrication. For example, capacitor performance can be improved byimproving the dielectric constant of the capacitor's dielectric layerand reducing leakage across the dielectric layer.

Ultra thin dielectric films can greatly affect the performance ofsemiconductor devices. Ultra thin films are normally used as dielectriclayers in semiconductor devices. Conventional ultra thin films anddielectric fabrication methods require high temperatures and are ofteninadequate to allow significant reduction of semiconductor device size.

Accordingly, there is a need in the art for an improved method offorming a dielectric layer or ultra thin dielectric film.

SUMMARY OF THE INVENTION

This need is met by the present invention wherein a method of forming anultra thin dielectric film or dielectric layer on a semiconductor deviceis disclosed. According to one embodiment of the present invention, asemiconductor device is provided. An oxide layer is formed over thesemiconductor device. A silicon-containing material is deposited over atleast a portion of the oxide layer. The oxide layer and depositedsilicon-containing material are converted to the ultra thin dielectricfilm by processing the deposited silicon-containing material and theoxide layer in a high density plasma.

According to another embodiment of the present invention, a method offorming a dielectric layer on a semiconductor device is disclosed. Asemiconductor device having an oxide layer is provided. Asilicon-containing material is vapor deposited over at least a portionof the semiconductor device. The deposited silicon-containing materialand the oxide layer are converted into the dielectric layer by utilizinga high density plasma.

According to another embodiment of the present invention a semiconductordevice is disclosed. The semiconductor device includes a substrate and adielectric layer. The dielectric layer is formed over the substrate byconverting vapor deposited silicon-containing material and a thin oxidelayer using a high density plasma.

Other methods and devices are disclosed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description of the present invention can be bestunderstood when read in conjunction with the accompanying drawings,where like structure is indicated with like reference numerals.

FIG. 1 illustrates a method for forming a dielectric layer according toone embodiment of the present invention.

FIGS. 2A, 2B and 2C illustrate a semiconductor device with a nitridedgate and its method of fabrication according to another embodiment ofthe present invention.

FIGS. 3A, 3B and 3C illustrate a semiconductor device and its method offabrication according to another embodiment of the present invention.

FIGS. 4A, 4B and 4C illustrate a semiconductor device and its method offabrication according to another embodiment of the present invention.

FIG. 5 illustrates a computer system that can use and be used withembodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a method for forming a dielectric layer or ultra thindielectric film according to one embodiment of the present invention. Asubstrate is provided at block 101. The substrate may comprise one ormore semiconductor layers or semiconductor structures which may defineportions of a semiconductor device. A semiconductor device may comprisea transistor, capacitor, electrode, insulator or any of a variety ofcomponents commonly utilized in semiconductor structures. Asilicon-containing material is vapor deposited over the substrate from asilicon source at block 102. As is noted below, the silicon-containingmaterial can be from a silazane or silane source such ashexamethyldisilazane (HMDS).

The dielectric layer or ultra thin dielectric film is formed bysubjecting the deposited silicon-containing material to a high densityplasma at a low temperature at block 103. For the present invention, alow temperature is defined as a temperature less than 300° C. A “highdensity plasma” is a plasma containing a higher density of ions incomparison to a normal plasma. Normal plasma has an ion concentration inthe range of 10⁹ ions/cm³ whereas high density plasma generally has aion concentration of 10¹¹ to 10¹² ions/cm³ (1000 times higher comparedto normal plasma). Silicon atoms of the deposited material react withions of the high density plasma. The high density plasma contains H₂,NH₃, N₂, O₂, O₃, N₂O or NO which are converted to ions or activatedspecies by the high density plasma.

During the process of subjecting the deposited silicon-containingmaterial to a high density plasma, the plasma can be remote or incontact with the wafer. The resulting film can be a nitride, oxynitrideor oxide film with specific electrical properties, depending on the typeof high density plasma used. Some examples of silicon-containing sourceswhich may be used are hexamethyldisilazane (HMDS),tetramethyldisilazane, octamethylcyclotetrasilazine,hexamethylcyclotrisilazine, diethylaminotrimethylsilane anddimethylaminotrimethylsilane, however other silicon-containing sourcesmay be used.

According to the remote plasma process of the present invention, theplasma is generated with microwaves or another form of conventionalplasma generating energy. Specifically, a wafer or substrate is placedin a chamber. Gases such as H₂, NH₃, N₂, O₂, O₃, N₂O and NO are exposedto plasma generated outside of the chamber to create the activatedspecies, such as H₂, NH₃, N₂, O₂, O₃, N₂O or NO ions. The plasma doesnot come into physical contact with the wafer or surface of thesubstrate which, in this case, is the silicon-containing material. Theactivated species are subsequently pumped into the chamber. This canreduce or prevent damage to the substrate or device.

Suitable remote plasma process parameters for a microwave plasma sourceinclude a power source of 500 W to 5 KW, a gas flow rate of 0-5000cm³/min and a pressure of 100 mT to 50T.

The contact plasma process is also referred to as a direct plasmaprocess. The wafer containing the semiconductor device is placed in achamber and the high density plasma is generated in the chamber,creating activated species. The plasma comes into direct contact withthe wafer. Exemplary parameters include a power source of 100 W to 4 kW,gas flow rate of 0-5000 cm³/min and a chamber pressure of 500 mT to 5 T.

FIGS. 2A, 2B and 2C illustrate a semiconductor device with a nitridedgate according to another embodiment of the present invention. FIG. 2Ashows the semiconductor device having a substrate 201 and a gate oxide202 prior to depositing a silicon-containing material from a siliconsource such as HMDS. The substrate 201 is of a semiconductor materialsuch as, but not limited to silicon. The gate oxide 202 is formed overthe substrate 201. FIG. 2B shows the semiconductor device having thesubstrate 201, the gate oxide 202 and a silicon containing material 203,after depositing the silicon containing material 203. The siliconcontaining material 203 has been vapor deposited over the gate oxide202. FIG. 2C shows the semiconductor device after the silicon containingmaterial 203 has been subjected to high density plasma (HDP) 204 andincludes the substrate 201 and an oxynitrided gate 205. The siliconcontaining material 203 can be subjected to the HDP remotely ordirectly. The gate oxide 202 and the silicon containing material 203have been converted into the oxynitrided gate 205 by the HDP 204. TheHDP 204 can include any activated species of plasma that converts thesilicon containing material 203 and gate oxide 202 into the oxynitridedgate 205. Some examples of precursors used in such plasmas fornitridation are NH₃, N₂, and N₂+H₂. The oxynitrided gate 205 has athickness of less than 30 Å and is comprised of Si₃N₄ or SiO_(x)N_(y).

FIGS. 3A, 3B and 3C illustrate a semiconductor device according toanother embodiment of the present invention. FIG. 3A shows thesemiconductor device having a substrate 301, a lower electrode 302 and anative oxide 303 prior to depositing a silicon layer 304. The substrate301 is of a semiconductor material such as, but not limited to silicon.The lower electrode 302 is formed over the substrate 301. Typically, thenative oxide 303 is formed over the lower electrode 302. The nativeoxide 303 naturally occurs on the lower electrode 302. In otherembodiments, an oxide layer can be grown or deposited instead of using anative oxide layer. FIG. 3B shows the semiconductor device having thesubstrate 301, the lower electrode 302, the native oxide 303 and asilicon layer 304. The silicon layer 304 is typically vapor depositedover the native oxide 303 from a silicon source such as HMDS. FIG. 3Cshows the semiconductor device after the silicon layer 304 has beensubjected to HDP 306 and includes the substrate 301, the lower electrode302 and a dielectric layer 305. The silicon layer 304 can be subjectedto the HDP 306 remotely or directly. The native oxide 303 and thesilicon layer 304 are converted into the oxynitrided gate 305 by the HDP306 by causing silicon atoms of the silicon layer 304 to react with thenative oxide and ions in the HDP 306. The HDP 306 can include anyactivated species of plasma that converts the silicon layer 304 and gateoxide 303 into the dielectric layer 305. Some examples of such plasmasare NH₃, N₂, and N₂+H₂. The dielectric layer 305 has a thickness of lessthan 30 Å.

FIGS. 4A, 4B and 4C illustrate a semiconductor device according toanother embodiment of the present invention. FIG. 4A shows thesemiconductor device having a substrate 401 and an oxide 402 prior todepositing a silicon-containing layer. The substrate 401 is of asemiconductor material such as, but not limited to silicon. The oxide402 is formed over the substrate 401. FIG. 4B shows the semiconductordevice having the substrate 401, the oxide 402 and a silicon-containinglayer 403, after depositing the silicon-containing layer 403. Thesilicon-containing layer 403 is typically vapor deposited over the oxide402. FIG. 4C shows the semiconductor device after the silicon containinglayer 403 has been subjected to HDP 404 and includes the substrate 401and a dielectric layer 405. The semiconductor device can be subjected tothe HDP remotely or directly. The oxide 402 and silicon-containing layer403 are converted into the dielectric layer 405 by the plasma 404. Theplasma 404 can include any activated species of plasma that converts thesilicon-containing layer 403 and oxide 402 into the dielectric layer405. Some examples of such plasmas are NH₃, N₂, and N₂+H₂. Thedielectric layer 405 can have a thickness of less than 30 Å.

FIG. 5 is an illustration of a computer system 512 that can use and beused with embodiments of the present invention. As will be appreciatedby those skilled in the art, the computer system 512 would include ROM514, mass memory 516, peripheral devices 518, and I/O devices 520 incommunication with a microprocessor 522 via a data bus 524 or anothersuitable data communication path. These devices can be fabricatedaccording to the various embodiments of the present invention. Forexample, mass memory 516 can comprise memory cells having at least oneultra thin dielectric film formed according to one embodiment of theinvention.

Dielectric layers or ultra thin dielectric films fabricated using thepresent invention can be used for a variety of purposes. Some examplesfollow, but embodiments of the present invention are not limited tothese. A dielectric layer can be used as a cell dielectric material. Adielectric layer can be used as a single dielectric in a capacitor,transistor or anti-fuse application. A dielectric layer can be used toform composite dielectric in a multi dielectric stack type spacer,capacitor, transistor or anti-fuse application. A dielectric layer canbe used to form a continuous low temperature barrier layer. A dielectriclayer can be used for low temperature conditioning for advanceddielectrics such as Ta₂O₅ and BST. A dielectric layer can be used for alow temperature post metal barrier layer or interconnect conditioning toreduce oxidation.

For the purposes of describing and defining the present invention,formation of a material “on” a substrate or layer refers to formation incontact with a surface of the substrate or layer. Formation “over” asubstrate or layer refers to formation above or in contact with asurface of the substrate. Formation “in” a substrate or layer refers toformation of at least a portion of a structure in the interior of asubstrate layer. An “ultra-thin film” is a dielectric layer with athickness not greater than 10 microns and uniformity within 20% of itsaverage value.

Having described the present invention in detail and by reference topreferred embodiments thereof, it will be apparent that modificationsand variations are possible without departing from the scope of thepresent invention defined in the appended claims.

1. A semiconductor device comprising: a substrate having at least onesemiconductor layer; a first conductive layer formed over the substrate;a silicon-containing dielectric layer formed over the first conductivelayer at a low temperature; a second dielectric layer formed over thesilicon-containing dielectric layer; and a second conductive layerformed over the second dielectric layer.
 2. The semiconductor device ofclaim 1, wherein the second dielectric layer is comprised of a materialselected from the group comprising Si₃N₄, BST, and PZT.
 3. Thesemiconductor device of claim 1, wherein the second dielectric layer iscomprised of a material selected from the group consisting of Si₃N₄,BST, PZT, Al₂O₃ and WO_(x).
 4. A semiconductor device comprising: asubstrate having at least one semiconductor layer; an electrode formedover at least a portion of the substrate and having a native oxideformed on the electrode; a silicon-containing ultra thin dielectric filmformed over the electrode from deposited silicon-containing material anda native oxide of the electrode; and a second dielectric layer formedover the silicon-containing ultra thin dielectric film.
 5. Thesemiconductor device of claim 4, wherein the electrode is comprised of amaterial selected from the group comprising P—Si, SiGe and metal.
 6. Thesemiconductor device of claim 4, wherein the second dielectric layer iscomprised of Ta₂O₅.
 7. A semiconductor device comprising: a substratehaving at least one semiconductor layer; and an ultra thin dielectricfilm formed over the substrate by converting vapor depositedsilicon-containing material from a silicon source and a thin oxide layerusing a high density plasma to cause silicon atoms from the depositedsilicon-containing material and oxygen atoms of the thin oxide layer toreact with ions of the high density plasma.
 8. A semiconductor devicecomprising: a substrate having at least one semiconductor layer; and anultra thin dielectric film formed over the substrate by converting vapordeposited silicon-containing material from hexamethyldisilazane and athin oxide layer using a high density plasma.
 9. A semiconductor devicecomprising: a substrate; and a oxynitrided gate formed over thesubstrate by converting vapor deposited material from ahexamethyldisilazane source and a gate oxide layer into the oxynitridedgate by flowing an NH₃ plasma over the deposited material.
 10. Acomputer system comprising: at least one processor; a system bus; and amemory device coupled to the system bus, the memory device including oneor more memory cells comprising: a substrate having at least onesemiconductor layer; a drain formed in the substrate; a source formed inthe substrate; a first oxide layer deposited over the substratestretching from the drain to the source rail; a silicon-containing ultrathin dielectric film formed over the substrate from silicon-containingmaterial deposited over the substrate and the first oxide layer; and agate electrode deposited over the ultra thin dielectric film.